| Subject | Re: [firebird-support] How to check whether a table exists or not? |
|---|---|
| Author | Helen Borrie |
| Post date | 2009-05-06T21:57:39Z |
At 06:17 AM 7/05/2009, you wrote:
The main showstopper for this approach is that scripts are not programs. They are nothing but lists of dynamic SQL statements executed in occurrence order. You can't do conditional things in scripts and you can't intercept and act on exceptions.
But your approach of "first deleting [sic] the tables and named constraints if they exist" is fraught with failure, anyway. Constraints create dependencies. Dependencies cause drop and alter statements to fail. Even if they don't fail, uncommitted metadata actions can have untoward effects on metadata that's entailed by later statements in a script unless you've planned this perfectly.
./heLen
>I am putting together my first database script for Interbase 7.5. Since I am still in development, I would like the script to first delete the tables and named contraints IF they exist. How might I do that?FYI, in SQL you DROP metadata objects and you DELETE data.
The main showstopper for this approach is that scripts are not programs. They are nothing but lists of dynamic SQL statements executed in occurrence order. You can't do conditional things in scripts and you can't intercept and act on exceptions.
But your approach of "first deleting [sic] the tables and named constraints if they exist" is fraught with failure, anyway. Constraints create dependencies. Dependencies cause drop and alter statements to fail. Even if they don't fail, uncommitted metadata actions can have untoward effects on metadata that's entailed by later statements in a script unless you've planned this perfectly.
./heLen